The present invention relates to emergency lighting units, and, more particularly, to such lighting units which may be substantially concealed in a building surface.
Emergency lighting units are widely employed in commercial and industrial buildings to provide illumination in the event of failure of normal power. Such units employ lamps which are oriented to illuminate passages to exits and are powered by direct current obtained either from internal batteries or from a decent conduit connected to a central battery bank. During normal power conditions, the batteries are charged by a charging circuit.
Such emergency lighting units are generally surface mounted and, despite substantial design efforts, detract from the otherwise planar surface characteristics of the rooms in which they are mounted. Since they are exposed, they are subject to environmental conditions and can be damaged by vandals or by accident as a result of operations within the rooms in which they are placed.
In an effort to improve the physical appearance of the rooms in which placed and to minimize the opportunity for injury to the emergency lighting units, there has been interest in providing units which could be concealed in the ceiling and only moved into an operative position in the event of a failure of the AC power supply. Attempts to produce such structures are illustrated in Gow U.S. Pat. No. 5,025,349 granted on Jun. 18, 1991 and Minter et al U.S. Pat. No. 4,802,065 granted on Jan. 31, 1989.
Units which require a substantial amount of energy to effect their movement from the concealed position to the operative position present the potential for malfunction, and could result in a possible hazard if the lamps were to be illuminated while still in their concealed or unexposed condition. Moreover, any obstruction impeding the opening movement could result in substantial damage to the drive assembly.
Accordingly, it is an object of the present invention to provide a novel concealed emergency lighting unit which will drop down to the open or functioning position, principally under the force of gravity.
It is also an object to provide such an emergency lighting unit which can be fabricated relatively easily from components which themselves can be readily fabricated or purchased.
Another object is to provide such a lighting unit which is attractive and which is readily adapted to use either with internal battery power or with DC current from an external battery supply.